Method and apparatus for improving efficiency of vane pumps



Dec. 26, 1967 c. E. ADAMS ETAL 3,359,914

METHOD AND APPARATUS FOR IMPROVING EFFICIENCY OF VANE PUMPS Filed Sept, 27, 1965 5 Sheets-Sheet 1 FIG. I

FIG. 2

CECIL E. ADAMS BY RANDALL E. GRIFFITH WM wWv W INVENTORS. I

E- ADAM Dec. 26, 1967 c. s ETAL 3,359,914

METHOD AND APPARATUS FOR IMPROVING EFFICIENCY OF VANE PUMPS 5 Sheets-Sheet 2 Filed Sept. 27, 1965 IOI loo 59 FIG. 4

IOI

0 T N E V W.

' CECIL E. ADAMS BY RANDALL E.GR|FFITH -W d,MO-W+W Dec. 26, 1967 CE. ADAMS ETAL METHOD AND APPARATUS FOR IMPROVING EFFICIENCY OF VANE PUMPS Filed Sept. 27, 1965 heets-Sheet 300 PSI/ PSI I600 I800 SPEED- RPM FIG. 8

SPEEDRPM FIG. 9

WM,MM+W

Filed Sept. 27. 1965.

Dec. 26, 1967 c. E. ADAMS ETAL 3,359,914

METHOD AN PPARA FOR IMPROVING EFFI NGY o ANE PUMPS heets-Sheet 4 INVENTORS. CECIL E. ADAMS RANDALL E. GRIFFITH Dec. 26, 1967 c. E. ADAMS ETAL 3,359,914

METHOD AND APPARATUS FOR IMPROVING EFFICIENCY OF VANE PUMPS Filed Sept. 27, 1965 5 Sheets-$116M 5 FIG. l6 FIG. I?

FIG. I8

I INVENTORS. CECIL E. ADAMS RANDALL E. GRIFFITH United States Patent 3,359,914 METHOD AND APPARATUS FOR IMPROVING EFFICIENCY OF VANE PUMPS Cecil E. Adams, Columbus, and Randall E. Griflith, Westerville, Ohio, assignors to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Filed Sept. 27, 1965, Ser. No. 4%,220 20 Claims. (Cl. 103-136) This invention relates to hydraulic pumps and, more particularly, to a method and apparatus for improving the efliciency and performance characteristics of vane type pumps. Radial vane pumps are the most common variety of vane pump and, therefore, this invention will be explained as applied to a radial vane pump although it should be understood that this invention is equally applicable to axial vane pumps.

Radial vane pumps incorporate a plurality of radially movable equiangularly spaced vanes mounted in slots in a rotor. These vanes engage the inner cam surface of a fixed cam ring or stator as they are rotated by the rotor. As is well known, a quantity of fluid from the suction or intake port of the pump is supplied to a zone located between each pair of vanes as the leading vanes of each pair pass the intake port. The entrapped liquid then is passed through an intermediate transfer zone of the pump and to the outlet or pressure port. As the vanes pass the pressure port, they are forced inwardly by the cam ring to reduce the capacity of the zone between the two vanes so that the entrapped liquid is forced out the pressure port.

One objective of this invention has been to prevent harmful results caused by high velocity liquid which blows by the vanes in a vane pump.

Another objective of this invention has been to improve the performance characteristics of vane pumps, and specifically to increase the maximum operating speeds and pressures of radial vane pumps.

Theoretically, the volumetric capacity of a radial vane pump may be computed methematically. In reality, however, the computation is not accurate because of leakage which occurs around the edges of the vanes and as a result of which liquid in the high pressure zone forces its way back into the low pressure zone. This leakage, of course, results in pump inefficiency and reduced pumping capacity.

Traditionally, attempts to decrease vane leakage and increase pump performance have involved efforts to form a more perfect seal between the vanes and the pump cam ring. This invention, however, is predicted on a new concept or approach to the problem. Specifically, it is predicated at least in part upon the realization that some clearance, however slight, must exist between the rotating vanes and the stationary components of the pump if the vanes are not to seize, gall or otherwise cause the pump to fail. Bearing in mind that some finite minimum clearance must exist and further that leakage will inevitably occur through these clearance gaps, and will increase when the pump is operated at high temperature and/ or high pressure, this invention is predicated upon the concept of diverting the leakage liquid away from the trailing transfer chamber or diverting it through a flow path operable to substantially reduce its velocity before it enters the trailing or lower pressure transfer chamber.

We have found it surprisingly advantageous to reduce the velocity and thus the kinetic energy of the blow by to a minimum and then to use this liquid in filling the trailing transfer chamber, although the liquid may be diverted to tank or to the pump intake port if so desired.

The fact that this diversion of the blow by liquid results "ice in better performance characteristics and more efficient pumps has been conclusively established in tests in which pump delivery '(gallons per minute) as a function of rotor speed was compared with the delivery of an otherwise similar pump not equipped with the features of this invention. These tests established that at high speeds, temperatures and pressures, pumps having the diversion features of this invention continued to operate at deliveries or capacities much greater than that at which the comparison pumps failed.

It is our present belief that these improved results can be explained in part by the more complete filling of the transfer chamber which results from such diversion of the blow by liquid. The blow by liquid has a great deal of kinetic energy as it starts to pass at high speed over the leading edge of the vanes. In the prior art this energy is dissipated in the trailing transfer chamber where it causes turbulence and cavitation. Because this turbulence occurs during the filling cycle of the transfer chamber, it interferes with the filling and thus decreases the volumetric or delivery efficiency of the pump. Whenever the transfer chamber is not filled, there is a resulting uneven pressure pattern as the trailing edge of a vane breaks from the pump transfer zone into the exhaust or pressure port zone. At the instant of break over, high pressure liquid from the pressure port spills over the trailing lip to suddenly increase the pressure in the unfilled transfer zone and, at high speeds, temperatures and/ or pressures, the life of the pump will be shortened by reason of the resulting rippling of the cam ring or galling between the vanes and the cam ring and/ or erosion of the internal operating parts of the pump.

Another objective of this invention has been to provide blow by liquid diversion in a vane pump wherein the diversion structure is valved to open and thereby decrease the detrimental effects of liquid blow by past a vane when the vane is passing through a transfer zone and which is valved to close and thereby minimize leakage past the vane when the vane is passing through a sealing zone.

Another objective of this invention is to provide means for preventing high temperature and/or high pressure cavitation in a vane pump caused by the uncontrolled leakage of liquid past a vane which leakage interferes with the complete filling of the spaces behind the vane, the means collecting high velocity liquid which otherwise would blow by the vane of the hydraulic pump, reducing the velocity of the collected liquid, then utilizing the liquid by directing it to behind the vane thereby to assist the complete filling of the space behind the vane.

These and other objects and advantages of this invention will be more readily apparent from the following description of the drawings in which:

FIGURE 1 is a cross-sectional view of a three-area radial type vane pump which incorporates the invention of this application,

FIGURE 2 is a view in elevation of the movable port plate or cheek plate of the pump, the view being taken along line 2-2 of FIGURE 1 and showing the ports and passageways therein,

FIGURE 3 is a view taken along line 3-3 of FIG- URE 1,

FIGURE 4 is a side-elevational view of one vane of the pump of FIGURE 1,

FIGURE 5 is a crosssectional view of fragments of the cam ring and rotor of the pump of FIGURE 1 illustrating. the manner in which the rotor and vane construction cooperate to form valving for controlling the flow of diverted liquid therethrough, the vane being shown in the position in which the valve is closed,

FIGURE 6 is a view similar to FIGURE 5 but showing the vane in a position in which the valve is open,

FIGURE 7 is a perspective view of a vane used in the pump of FIGURE 1,

FIGURE 8 is a graph showing the performance of a constant volume radial vane pump not including the features of this invention,

FIGURE 9 is a graph showing the'performance of a constant volume radial vane pump of the same capacity and design as the one used to prepare the graph of FIG- URE 8 but including the features of this invention,

FIGURE 10 is a view in section of a check or port plate illustrating a second embodiment of the invention of this application,

FIGURE 11 is a view similar to FIGURE 3 illustrating a radial vane pump incorporating the cheek plate of FIGURE 10,

FIGURE 12 is a view of fragments of a rotor and ca m ring useable in the pump of FIGURE 1, this rotor including fluid diverting passageways leading from adjacent the bottom of each of the vane slots in the rotor to the periphery of the rotor at the trailing side of the vane slots,

FIGURE 13 is a view taken on line 1313 of FIGURE 12 and showing the location of the outlet fluid passageways seen in FIGURE 12.

FIGURE 14 is a view similar to FIGURE 12 but showing a different vane configuration,

FIGURE 15 is a perspective view of the vane of FIG- URE 14,

FIGURE 16 is a view similar to FIGURE 12 illustrating another embodiment of the invention of this application, the vane in this figure being in a valve open position,

FIGURE 17 is a view similar to FIGURE 16 but illustrating the valving in the close position,

FIGURE 18 is a perspective view of the vane of FIG- URE 16.

The invention described and claimed herein is applicable to vane pumps of any type. It has been illustrated and described herein in connection with a three area radially movable vane pump which utilizes hydraulic pressure to hold the vanes radially outwardly. It should be appreciated, however, that this invention is equally applicable to all vane type pumps, irrespective of the means used to urge the vanes outwardly against the cam element.

Referring now to FIGURES 1-7 of the drawings, it will be seen that the pump 10 includes a body or casing 20 formed by a casting or body section having a generally cylindrical hollow interior and an end ca or block 21 having a cylindrical boss 22 which telescopes into the open end of the body 20 and is sealed thereto by an O-ring 23 received in a groove in the end cap 21. The end cap 21 is secured to the body by four screws (not shown).

The end wall 26 of the body 20 opposite the cap 21 includes a bore through which the pump operating shaft 27 extends. Shaft 27 is supported for rotation in this bore by a ball bearing 28 which is secured against axial movement in the bore by a flange 29 on the casting and a snap ring 30 which is received in a groove in the bore. The end of the shaft 27 which is within the housing is carried for rotation in a needle type roller bearing 31 fitted within a central bore or recess in the end cap 21.

Boss 22 of the end cap 21 is finished to form a flat cheek or port plate surface which abuts a flat end surface of a cam ring 32. It may be mentioned here that the easing or housing and the cam ring are frequently termed in the art as the stator, and frequently the cam ring per se is termed as the stator. It will therefore be understood that the term stator as employed in the claims hereof is to be construed as meaning the combination of the housing and the cam ring, the cam ring itself, or the equivalent elements in any unit wherein the housing and the stator are made integral as is sometimes done in the art.

A liquid intake or suction port 24 extends radially inward and communicates with a pair of internal annular grooves or channels 37, 38 formed within the body 20, as shown in FIGURE 1, which encircle the internal cavity within the body. The channels 37, 38 distribute liquid from the intake port 24 to pumping spaces to be described. The cam ring 32 is supported radially by an annular rib 40 formed in the body between the channels 37, 38.

The cam ring 32 encircles or encompasses a rotor 42 which is mounted upon the shaft 27 for relative axial movement through a relatively loose splined joint connection which allows proper running alignment between the rotor and the adjacent cheek plates. The width of rotor 42 is no greater and is preferably of the order of .0015 inch less than the axial dimension of the cam ring 32 in order that it may rotate without undue friction against the surface of boss 22 on one side and the face of a floating cheek plate 43 on the other side. The rotor 42 is provided with a plurality of radially extending vane slots in each of which there is a vane 45. Each vane is likewise .0015 inch less wide than the cam ring in order that there will be a total clearance of .0015 inch between the vanes and the cheek plate 43 and the vanes and the end cap 21. Each vane 45 is urged radially outwardly against the inner surface 46 of cam ring 32 by hydraulic pressure means which is the subject of a co-pending application of Cecil B. Adams and Gerald E. DeVillers, Ser. No. 296,017 filed July 18, 1963, now Patent No. 3,223,044 and assigned to the assignee of this application.

The cam ring 32 has a cylindrical external surface. Its interior surface 46 provides a balanced type construction in which there are diametrically opposite pairs of low pressure suction or inlet Zones 47, transfer zones 48, high pressure or exhaust zones 49, and sealing zones 50 (see FIG- URE 3). For simplicity in the drawings, only one-half of the cam ring is illustrated in FIGURE 3 although it should be understood that an identical construction would exist on the other side of the broken line of this figure.

In order to provide these opposed pairs of zones, the interior or cam surface 46 of the cam ring 32 is formed in part upon two arcs 51 (only one of which is illustrated) of equal radii struck from the axis of shaft 27, which extend across the transfer zone 48 and two arcs 52 of shorter radii than the first mentioned arcs and which extend across the sealing zones 50. The arcs 52 are of slightly greater radii than the rotor so that they nearly touch the rotor 42. The arcs 51 and 52 are connected by cam portions or ramp surfaces 53, 54 which extend across the low pressure zones 47 and the high pressure zones 49 respectively.

The cheek plate 43 is finished to a smooth, flat surface 58 on the side thereof which abuts the cam ring 32, and is provided with a central bore 59 surrounded by a cylindrical boss 61 which extends into the bore in the end wall 26 of the body 20 and is sealed thereto by a pair of O-rings 62 contained in a pair of spaced grooves in the boss 61. The central bore 59 in the cheek plate 43 receives an oil seal 63 which engages the shaft 27 and prevents the loss of liquid to the outside of the body or housing 20 of the pump, and which also prevents the entrance of air into the interior of the body. The radially outermost cylindrical [peripheral surface of cheek plate 43 is sealed to the body 20 by means of an O-ring 65.

The cheek plate 43 is urged axially toward the rotor 42 by the action of fluid pressure directed from fluid discharge ports within the pump through passageways 66 and 82 to an annular space or pressure chamber 68 formed between the body and the outer face of the cheek plate. The check plate 43 functions in the nature of an axially movable, non-rotatable piston under the pressure supplied by fluid in chamber 68.

When the pump is operating, liquid flows from the inlet or suction port 24 through the grooves 37, 38 and circumferentially around the cam ring 32 to two ports spaced apart at which the fluid flows axially and around the cam ring 32 and enters inlet or suction ports 72 formed in cheek plate 43 and inlet or suction ports (not shown) formed in the end cap 21. The inlet port of the cheek plate 43 and end cap 21 are axially aligned and are identical in shape. Each pair of ports opens into the suction zone 47 adjacent a cam portion 53 of the cam ring 32. The ports 72 each join radially inwardly extending passages which terminate in axially aligned ports 74 in both the cheek plate 43 and the end cap 21. The ports 74 communicate with the inner ends 86 of the vane slots in the rotor 42 as the slots pass the port 74.

As shown in FIGURES 1 and 2, the cheek plate 43 includes two crescent shaped high pressure or exhaust ports 77 which are spaced 1-80 apart and at 90 with respect to each of the inlet or suction ports 72. Similarly, high pressure ports 76 are formed in the end cap 21, are also crescent shaped, and are axially aligned with the ports 77 in the cheek plate. These exhaust ports open into the pressure zones 49 adjacent the cam portion 54 of cam ring 32. Each of the exhaust ports 76, 77 also includes a radial inward extension which terminates in a port 78 that communicates with the inner ends 86 of the vane slots in the rotor 42 as the slots pass ports 76, 77. The ports 77 are connected with the exhaust, high pressure or outlet port 25 by a passageway 79 in the end cap 21.

With reference to FIGURE 3, it Will be noted that the cam surface 46 comes into close proximity to the rotor 42 at the two diametrically opposite arcuate sealing zones 56 in which the cam surface has a substantially constant radial spacing from the rotor. At the inlet ports 72, the cam surface 46 progressively recedes from the rotor periphery in the direction of vane movement. In the transfer zones 48, the cam surface also is a substantially constant radial spacing from the rotor, and adjacent the high pressure ports 77, the cam surface 46 progressively approaches the rotor, until it again comes into close proximity to the 'rotor in the sealing zones 50. Thus, fluid is drawn into the spaces or fiuid transfer pockets between the successive vanes as these spaces become larger when the vanes move through low pressure zones 47 and it is displaced positively 'as these spaces contract when the vanes move through high pressure zones 49 to effect pumping action.

, The cheek plate 43 is provided with radial or transverse passageways 82 (FIGURE 1) which communicate between the high pressure port 77 formed in the cheek plate and the axial passageway 66 formed therein. Through these passageways 82 and 66 liquid at the outlet pressure of the pump is conducted to the chamber 68 on the outer side of the cheek plate whereby a force acts on the cheek plate to hold it in sealing engagement with the cam ring 32.

To effect an efficient pumping action, it is necessary to maintain continuous engagement of the vanes 45 with the cam surface 46, regardless of changes in the arcuateness of the cam surface. Discontinuities in the engagement of the individual vanes with the cam surface 46, or intermittant separation of the vanes from the cam surface 46, are not only a cause of inefiicient pumping but can cause serious premature wear on the pumping structure. Unless there is sealing between the edge of a vane in the transfer zone and the cam surface, liquid at high pressure on the forward side of the vane will blow by over the vane into the zone of low pressure on its opposite side, thereby disturbing the intake of liquid at the suction port and in the suction zone and reducing volumetric efficiency.

Referring to FIGURES 1, 3 and 7, it will be seen that each of the vanes 45 is provided with peripheral grooves 84 formed between its leading and trailing faces along opposite sides and the outer ends of the vane. In addition to these grooves, each vane is provided with a pair of radial apertures 85 at opposite ends of the vane connecting the inner end with the outer end. These grooves 84 and apertures =85 insure that the pressures acting on the exposed radially opposed end surfaces of the vane are substantially equal at all times, pressure on the upper end of the vane being reflected through the grooves 84 6 and apertures into the enlarged rounded inner end 86 of the vane slot.

One or more radial bores 88 is formed in the rotor 42 at the inner end of each vane slot. The bores 88 communicate at their inner ends with an annular passageway or groove 89 which extends completely around the rotor 42, and which is sealed with respect to the shaft 27 so that liquid can flow either into or out of the passageway 89 only through the bores 88.

Passageway 89 is sealed by a hollow cylindrical sleeve 90 which is sealingly pressed into a recess in the rotor bore. Power is transferred by a spline connection to shaft 27 as at 91. By the passageway 89, the inner ends of the bores 88 are in constant communication, and are at the pressure in passageway 89.

In each bore 88 there is provided a tubular piston valve element 92 which is generally cylindrical and which includes an internal bore 93. Each valve element 92 is slidable in its bore 88 but is closely fitted thereto so that leakage of liquid along the walls of the element 92 is minimal. The outer end of each piston element 92 is relieved or tapered as at 94, and forms a valve with flat inner end of the vane 45 which regulates the admission of liquid to bores 88 and passageway 89. The length of valve element 92 is such as to permit it to move into and out of engagement with the flat surface 95 of the vane 45.

In the operation of the pump, the valve elements 92 function in the manner of check valves. Whenever the pressure at the inner end 86 of a vane slot, which pressure acts upon the outer end of the valve element 92, exceeds sufiiciently the pressure in passageway 89 acting on the inner end of the valve element 92 to urge the element toward the vane, valve element 92 is moved inwardly in its bore, opening the valve 94 so that liquid in the vane slot flows inwardly to the passageway 89 to restore, maintain or increase the pressure in passageway 89. This action can occur whenever the vane slot 84 registers or connects with a high pressure zone adjacent a pressure port 78. The pressure at the pressure zone 49-78 is usually the highest in the pump. The pressure in the passageway 89 is usually lower by some amount than the pressure in the ports 78.

By the above-described action of the piston valve elements 92, the pressure in passageway 89 is maintained substantially constant for any given pressure at the pressure ports 78. When a given vane is aligned with a suction port 74, the pressure in passageway 89 exceeds the pressure at the outer end of the element 92 associated with that vane and the element 92 is held against the bottom 95 of the vane to close valve 94 and liquid cannot escape through bore 93. When a vane is moving across the suction zone 47 and/ or a transfer zone 48, the pressure at the inner and outer end of the vane is less than the pressure within the passageway '89 and the bore 93 in the piston valve 92 and therefore the pressure acting on the inner end of the piston valve and the area on the inner end of the vane defined within the bore 93 urges the vane outwardly into a positive engagement with the cam ring.

Excepting when a vane is out of pressure zone 4948, force for holding the vane outward is supplied by pressure acting on the end area of the element 92 and on the vane in the bore 93 which together constitutes a third area means. This force varies with the pressure difference at opposite ends of each element 92 which in turn varies with the position of the vane with relation to the suction and pressure ports.

The foregoing three area vane type pump is completely described in the above-identified co-pending application and forms no part of the invention of this application. The invention of this application is predicated upon the diversion of liquid as it blows by a vane located in the transfer zone, as is fully described herein.

As mentioned above, clearance of approximately .0015

inch is provided along the sides of the vane between the vane and the cheek plate 43 and the vanes and the end cap .21. In other words, when the vanes are centered between the cheek plate 43 and the end cap 21, 00075 inch clearance exists on each side of the vane. It is through these clearance gaps that most of the blow by occurs in the transfer zone since the three area force for holding the vane outwardly forms a very effective seal between the vanes and the cam ring 32.

Since clearance must exist between the sides of the vanes and the cheek plate 43 and end cap 22, blow by is going to occur through these side clearance spaces whenever there is a pressure differential on opposite sides of the vane, as there is when the vane is located in the transfer zone. This blow by ordinarily consists of a very high velocity stream of fluid squirting past the sides of the vanes to create turbulence and gasification on the trailing side of the vane 4-5 located in the transfer zone. The gasification and turbulence interfere with the filling of the transfer chamber on the trailing side of the vane with the result that cavitation occurs and the pocket is incompletely filled when it reaches the pressure port 77 or the pressure zone 49 of the cam plate. Our own hypothesis is that at the instant the trailing side of the vane 45 crosses from the transfer zone 48 into the pressure zone 49, liquid from the high pressure zone spills over the trailing outer corner of the vane 45 in an attempt to fill the cavitated pocket or transfer chamber. This hypothesis is confirmed by the fact that after having been run for some extended period of time at high speeds, temperatures and pressures, the cam ring 32 displays burn marks and even eroded areas in the metal in the area where the transfer zone 48 meets the pressure zone 49. Additionally, the trailing upper edges 97 of the vanes have burn marks or are worn down considerably below the level of the forward lips thereof.

Since there is no way of avoiding blow by along the sides of the vane, this invention is predicated upon the concept of controlling that blow by so as to minimize its detrimental effects. To this end, means are provided to prevent the high pressure liquid, after it passes the leading side edges of the vane, from squirting past the trailing edge and dissipating its speed or kinetic energy in the trailing transfer chamber.

In the preferred embodiment illustrated in FIGURES 1-7, the velocity of the blow by liquid is first reduced by directing the blow by liquid into a tortuous passageway or chamber having a large volumetric capacity wherein the velocity of the blow by liquid is reduced, and then passing the liquid to the trailing transfer chamber on the trailing side of the vane to assist in filling that chamber. The mentioned passageway for each vane includes a bore 98 in each vane extending from its top edge through approximately the depth of the vane. Additionally, a large diameter shallow bore or port 99 is counterbored in the trailing side of each vane and connected with the radial bore 98 via a small transverse bore 100 located at the inner side of the bore 99. Thus, the bore or port 99 on the trailing side of the vane communicates with the groove 84 in the sides and top of the vane via the transverse bore 100 and radial bores 98.

In operation, the radial bore 98, transverse bore 100, and port 99 cooperate to provide diversion porting or passageway means operable to dissipate the velocity of the high pressure liquid which has squeezed by the leading edge or leading lip 101 of the vane 45 in the transfer zone 48 before that liquid can enter the chamber on the trailing side of the vane. This high pressure liquid squeezing by the leading lip 101 of the vane tends to create a pressure rise in the groove 84. However, this pressure rise is offset by liquid flowing through the bores 98, 100 and port 99 to the trailing side of the vane. In other words, the liquid flows through the flow path of least resistance, via the groove 84, passageways 98, 100 and port 99 to the trailing side of the vane rather than through the clearance space between the trailing lip 97 of the vane and the stator. Flowing via this diversion porting or velocity reducing means 84, 98, 100, 99, rather than through the clearance gap between the trailing lip 97 of the vane and the stator, the kinetic energy or speed of the liquid is reduced as the liquid enters the port 99 in the trailing side of the vane 45 and before it passes into the trailing chamber. When it does enter the chamber, its velocity has been reduced so that the liquid does not cause turbulence and gasification with the result that it assists in filling the chamber on the trailing side of the vane rather than inhibiting the filling of that chamber.

The position of the port 99, medially the length of the vane, is such that it tends to cause liquid to fill the trailing chamber in the area of greatest cavitation at the back of the vane.

As may be seen in FIGURE 5, the port 99 and the vane slot in the rotor 42 cooperate to form a closed valve in the diversion porting when the vane is located in a sealing zone 52. We prefer to close this valve 99, 42 when the vane is in a sealing zone because of the tendency for the vane to cant or cock forwardly in the vane slot of the rotor when the vane is in a sealing zone 52. When the vane cants forwardly, the forward lip 101 of the two lip vane separates from engagement with the cam ring 32 with the result that, in the absence of the valve, a leakage path would be established through the diversion porting to the groove 84 beneath the forward lip 101 of the vane to suction. The valve thus reduces cross port leakage through the diversion porting when the vane is in a sealing zone.

A primary advantage of this invention is the resulting increased pressure and volumetric capacity of a given size pump. In other words, a pump including this invention is able to operate at much higher speeds, temperatures and pressures than an identical pump without the invention. This is illustrated graphically in FIGURES 8 and 9.

Referring first to FIGURE 8, the speed in revolutions per minute is plotted on the graph abscissa and the delivery in gallons per minute is plotted on the graph ordinate of a standard radial vane pump of the type disclosed in the above identified application Ser. No. 296,017. Each of the lines 105, 106, 107 and 108 represents a plot of speed against delivery at a selected exhaust pressure. As the pressure increased, the end point of the plot at which the delivery fell or the pump failed decreased. In the case of lines 107 and 108 of FIGURE 8, the end portions of the lines are shown in dashed lines to indicate that the pump was chattering very badly before it failed.

The graph of FIGURE 9 is identical to that of FIG- URE 8 except that it represents the plot of speed versus delivery of a pump which incorporated the features of this invention. In other words, the pump used to prepare FIGURE 9 was identical to that used to prepare FIGURE 8 except that the former included the features of this invention and the latter did not. As may be seen in FIGURE 9, the end points of the graph or the points at which the tests were stopped when the pump was operating at 1750 and 2000 p.s.i., lines 109 and 110 respectively, are at least 50% higher in terms of the delivery of the pump than the end points or points of failure of identical pumps without the diversion porting. Even at lower pressures where diversion porting is not so critical, the pump continued to operate efficiently long after the pumps without the diversion porting had ceased to operate.

The tests indicated in FIGS. 8 and 9 of the drawings were all conducted at 220 F. with atmospheric pressure at the pump inlet and with the same oil.

Another advantage of our invention which is not illustrated graphically but which has been measured quantitatively, is the resulting quieter operation. A pump incorporating the diversion porting of this invention and operating at 1800 rpm. was found to be three to five decibels quieter than an identical pump without the diversion porting.

Referring to FIGURES 10 and 11 there is illustrated a second embodiment of the invention of this application. In this embodiment the diversion porting is provided through the cheek plate 1 43 rather than through the vanes. Aside from the cheek plate and vanes, the pump of this embodiment is identical to that of FIGURES 1 through 3 and therefore identical parts have been given identical numerical designations. The vanes 145 in this embodiment differ from the vanes 45 of FIGS. 1-7 only in that the vanes 145 lack the radial bore 98, transverse bore 100 and rear port 99. In all other respects, the vanes are identical.

The check plate 143 in this embodiment is identical to cheek plate 43 of the embodiment of FIGS. 1-7 except that it is provided with a pair of diametrically opposed diversion conduits 150, 151 (FIG. Each conduit 150, 151 is spaced the same radial distance from the axis of the drive shaft 27 as the bottom sections 286 of the vane slots in the rotor 42. These conduits establish communication between the face 158 of the cheek plate and the internal bore 159. The bore 159 is connected so that pump leakage flows either to the tank reservoir or to the pump inlet. Thus, when the vanes pass the conduits 150, 151 or when the vane slots are in communication with the conduits 150, 151, a diversion flow path is established between the vane grooves 184 and the tank or inlet port.

Each conduit 1'50, 151 consists of a large, shallow bore 152 part way through the cheek plate and a smaller diameter orifice 153 extending the remainder of the way through the cheek plate. The diameter of the shallow bore 152 is such that it establishes communication between the bottom 1 86 of the vane slot in the rotor and the orifice 153 to tank whenever a vane is located in approximately the middle third .of the transfer zone. This may be clearly seen in FIGURE 11. When the vane breaks over into the pressure zone 49, the bottom 186 of the vane slot is out of communication with the shallow bore 152, and likewise, when the vane is in the suction zone 47, the bottom of the vane slot 186 is out of com- \munication or alignment with the bore 150. In other words, the diversion ports 150, 151 connect the vane groove 184 to tank or inlet pressure whenever the Vane slot in the rotor is sealed from the suction port or the pressure port.

It will be noted that the orifice 153 is much smaller in diameter than the bore 152 and therefore restricts the flow of fluid through the diversion porting 184, 186-, 152 and 153 to tan-k. The orifices 153 restrict the flow of diverted blow by liquid from the grooves 184 and thus maintain some back pressure on the liquid in the grooves 184. In the absence of this back pressure, foaming of the liquid in the grooves would result in erosion in the vanes and on the cam ring.

Referring now to FIGURES 12 and 13, there is illustrated still another embodiment of the invention of this application. In this embodiment, the pump is identical to that disclosed in FIGURES 1-3 except that the diversion porting is located in the vane and rotor rather than in only the vane. In this embodiment, those components which are identical to the components of the pump of FIGURE 1 have been given identical numerical designations.

In this embodiment, the vane 245 is identical to that illustrated in the embodiment of FIGURES 10 and 11. In other words it differs from the vane of FIGURE 1 only in that it does not include the diversion porting conduits 98, 100, and 99*. It does, however, have the peripheral groove 284 along its top edge and both of its side edges so that communication is established between the top of the vane and the bottom 286 of the vane slot in the rotor.

In the embodiment of FIGURES 12 and 13, the diversion porting which distinguishes this pump from that disclosed in FIGURES 1-7 consists of a conduit through the rotor which connects the bottom :arcuate portion 286 of the vane slot to the chamber on the trailing side of the vane 245. This diversion porting conduit consists of a pair of bores 290, 291 drilled through the rotor, bore 290 on a cordal line of the rotor from the trailing chamber into the arcuate section 286 of the vane slot, and the other bore 291 perpendicular to bore 290 and extending from the bore 290 to the surface of the rotor at a point closely adjacent to the trailing side of the vane. The end of the bore 290 adjacent the surface of the rotor is closed and sealed by a plug 292.

In operation, liquid under high pressure which blows by the leading edge or lip 293 of the vane enters the fluid filled chamber formed by the groove 284 where it is diverted through the groove and conduits 285 to the chamber 286 and subsequently through the conduit 290, 291 to the chamber on the trailing side of the vane which is filling with liquid. Referring to FIG. 13 it will be seen that the conduit 291 enters behind the longitudinal center of the vane in the area of greatest tendency to cavitate to assist in filling that area with fluid. In this way, the velocity of the blow by liquid passing the leading lips 293 of the vanes is reduced by the diversion porting before it enters the trailing chamber. In other words, it enters as a relatively low velocity stream rather than as a high speed stream flowing past the side clearance spaces between the trailing lip 294 of the vane and the cheek plate and end cap.

Referring to FIGURES 14 and 15, there is illustrated still another embodiment of the invention. This embodiment is very similar to that illustrated in FIGURES 12 and 13 and differs therefrom in that it incorporates a vane 345 which has only one lip or sealing edge in contact with the cam surface rather than a double lip. While we prefer to use double lip vanes in practicing this invention, it is equally applicable to a single lip vane of the type shown since most of the blow by occurs around the side edges of the vanes rather than across the top of the vane.

Each vane 345 of this embodiment has only a single lip on its top or cam engaging side but has two lips, 393, 394 at both ends. These lips are defined by a goove 384 milled into the end and extending from the bottom surface 395 of the vane 345 up to a point closely adjacent the top edge so that a rib 396 extends along the top of the vane in the plane of the side edges of the lips 393, 394.

The rotor 242 of the pump illustrated fragmentarily in FIGURES 14 and 15 is identical to that illustrated in FIGURE 12 and includes the diversion porting conduits 290, 291 connecting the bottom arcuate section 286 of each vane slot to the chamber on the tnailing side of the vane. Thus, in this embodiment, liquid flowing past the leading edge of lips 393 of the vane flows through the diversion path via groove 384, vane slot 286 and conduits 290, 2911 to the trailing side of the vane rather than passing the trailing side of the vane as a high velocity stream. The upper ridge or lip 396 prevents the blow by liquid from flowing past the leading lip 393 upwardly through the groove 384 and directly into the trailing chamber.

Referring to FIGURES 16, 17 and 18 there is illustrated still another embodiment of the invention of this application. This embodiment is very similar to that illustrated in FIGURES 12 and 13 except that it has the additional feature of a valve operable to minimize leakage from the pressure port to the inlet port when the vane is in the sealing zone.

The diversion porting of this embodiment is located in the vane 445 and the rotor 442. As may be seen in FIGURE 18, the vane 445 includes the groove 484 which extends across the top of the vane and along both sides so that the vane is of the two lip type. This vane differs from that illustrated in FIGURES l1 and 12 only in that it has a pair of small slots 490, 491 milled or otherwise machined out of the leading and trailing bottom sides of the vane approximately medially of the length of the vane. Only one slot 490 on the trailing side of the vane is functional but identical slots are provided on both sides in order that the vane may be assembled in the pump without attention to the proper orientation of the leading and trailing sides of the vane.

The diversion porting in the rotor consists of a bore 492 extending from the surface of the rotor on the trailing side of a vane into the bottom portion of the linear sec tion of the vane slot and a second bore 493 from the surface of the rotor closely adjacent the vane into the first bore 492. The first bore 492 is closed and sealed at the surface of the rotor by a plug'494.

Referring to FIGURE 16, it will be seen that liquid under high pressure which blows by the leading lip 495 of the vane when the vane is located in the transfer zone is diverted through the groove 484, the bottom 486 of the vane slot and the conduits 492, 493 to the trailing side of the vane. Thus, in this embodiment as in all those described heretofore, the diversion porting precludes substantially all direct blow by of liquid from the high pressure side of a vane located in the transfer zone to the low pressure or trailing side of the vane.

When the vane is located in the sealing zone, as illustrated in FIGURE 17, the diversion porting is sealed so that high pressure fluid on the trailing side of the vane cannot pass through the diversion porting up through the groove 484 and beneath the crack between the forward lip 495 of the vane and the cam ring 32 caused by canting of the vane 445. This valving action occurs as a result of the flat trailing surface of the vane passing over and sealing the entrance of the hole 492 into the vane slot. This valving action thus decreases leakage which would other wise occur from the high pressure side of the vane to the low pressure side when the vane is located in the sealing zone.

As has been brought out heretofore, the diversion porting of all of the embodiments illustrated in this application operate to increase the maximum delivery capabilities of the pump as well as increasing the pressures at which the pump is capable of operating at higher speeds and temperatures. Additionally, this diversion porting renders the pump much quieter in its operation.

While several embodiments of the invention of this application have been illustrated and described herein, those skilled in the art to which this invention pertains will readily comprehend various modifications and changes which may be made in the structure while still practising the inventive aspects of this invention. Therefore we do not intend to be limited except by the scope of the appended claims.

Having described our invention, we claim:

1. The method of improving a vane type hydraulic pump in which liquid under pressure from a high pressure zone leaks past a vane at a relatively high velocity through clearance gaps at edges of the vane to reach the low pressure zone behind the vane and prevents complete filling of said zone with liquid, said method comprising:

directing the flow of liquid after it begins to pass said vane through a velocity reducing means and then directing the reduced velocity liquid to behind the vane.

2. The method of improving a vane type hydraulic pump in which liquid under pressure from a high pressure zone leaks past a vane at a relatively high velocity through clearance gaps at edges of the vane to reach the low pressure zone behind the vane and prevents com plete filling of said zone with liquid, said method comprising:

diverting the flow of high velocity liquid after it begins to pass the leading edge of said vane, thereby preventing it from passing the trailing edge thereof.

3. The method of improving a vane type hydraulic pump in which liquid under pressure from a high pressure zone leaks past a vane at a relatively high velocity through clearance gaps at edges of the vane to reach the low pressure zone behind the vane and prevents complete filling of said zone with liquid, said method comprising:

reducing the velocity of the liquid after it begins to pass said vane through a velocity reducing means before it is able to cross the trailing edge of the vane and pass into the low pressure zone behind the vane.

4. The method of improving a vane type hydraulic pump in which liquid under pressure from a high pressure zone leaks past a vane at a relatively high velocity through clearance gaps at edges of the vane to reach the low pressure zone behind the vane and prevents complete filling of said zone with liquid, said method comprising:

venting the flow of liquid after it begins to pass said vane through a chamber in which the pressure is lower than the pump exhaust pressure and higher than the pump input pressure.

5. The method of improving a vane type hydraulic pump in which liquid under pressure from a high pressure zone leaks past a vane at a relatively high velocity through clearance gaps at edges of the vane to reach the low pressure zone behind the vane and prevents complete filling of said zone with liquid, said method comprising:

directing the flow of liquid after it begins to pass said vane to tank before it can enter the low pressure zone behind the vane.

6. The method of improving a vane type hydraulic pump in which liquid under pressure from a high pressure zone leaks past a vane at a relatively high velocity through clearance gaps at edges of the vane to reach the low pressure zone behind the vane and prevents complete filling of said zone with liquid, said method comprising:

collecting the liquid after it begins to pass said vane and before it passes the trailing edge thereof and causing it to enter said low pressure zone in a selected area thereof.

7. The method of improving a vane type hydraulic pump which includes a rotor carrying vanes which pass sequentially through an intake zone, a transfer zone, a high pressure outlet zone and a sealing zone, the said sealing zone being between an outlet zone and an intake zone, and wherein liquid tends to blow by vanes when said vanes are in a transfer zone and in a sealing zone, said method comprising:

diverting the flow of high velocity liquid through a diversion passageway after it begins to pass the leading edge of a vane in the transfer zone to prevent it from passing the trailing edge thereof and closing the diversion passageway when the vane is in the sealing zone thereby preventing cross portleakage through the diversion passageway.

8. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid transfer chambers defined between said vanes,

a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone, clearance gaps between said vanes and said stator, means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure on the liquid at said pressure port to a pressure substantially greater than that at said suction port whereby liquid pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid flows through said clearance gaps past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane, and

velocity reducing passageway forming means collecting and directing liquid blown by said leading edge to the zone of lower pressure behind said vane while reducing its velocity to reduce turbulence in said low pressure zone.

' 9. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid transfer chambers defined behind said vanes,

a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone,

clearance gaps between said vanes and said stator,

means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure on the liquid at said pressure port to a pressure substantially greater than that at said suction port whereby liquid pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid flows through said clearance gaps past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane,

and

means forming a passageway for directing liquid from the front to the rear of the vane while said vane is in a transfer zone to aid in filling the chamber behind the vane. 10. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a:stator presenting a cam surface and side walls for engagement by the outer ends of said vanes, liquid transfer chambers defined between said vanes, a suction port and a pressure port at circumfereutially spaced positions-between said rotor and said cam surattempt to reach the lower pressure chamber -behind said vane, and

means for reducing the velocity of the blow by liquid after it passes said leading edge and before it reaches the trailing edge of said vane so as to reduce turbulence in the liquid in the chamber behind said vane.

11. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid transfer chambers defined between said vanes,

a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone,

clearance gaps between said vanes and said stator,

means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure on the liquid at said pressure port to a pressure substantially greater than that at said suction port whereby pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid flows past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane, and I means for diverting the flow of liquid through a velocity reducing path into the low pressure zone behind the vane after it passes said leading edge and before it reaches the trailing edge of said vane.

12. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid transfer chambers defined between said vanes,

a suction port and a pressure port at circnmferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone,

clearance gaps between said vanes and said stator,

means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure on the liquid at said pressure port to a pressure substantially greater than that at said suction port whereby pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid blows by the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane, and

means for diverting the said blow by liquid to tank after it passes said leading edge and before it passes the trailing edge of said vane so as to prevent it from entering the chamber behind said vane.

13. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid trans-fer chambers defined between said vanes,

a suction port and a pressure port at circumferenti ally spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone,

clearance gaps between said vanes and said stator,

means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure on the liquid at said pressure port to a pressure substantially greater than that at said suction port whereby pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid flows through said clearance gaps past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane,

means for directing the flow of liquid to a zone of lower pressure than in front of said vane after it passes said leading edge and before it reaches the trailing edge of said vane, and

said directing means comprising a longitudinal groove along at least one side of each of said vanes and conduit means connecting said groove with said lower pressure zone, said directing means further including a valve operable to control liquid flow through said conduit means.

14. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid transfer chambers defined between said vanes,

a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone and a sealing zone,

clearance gaps between said vanes and said stator,

meansforrotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure on the liquid at said pressure port to a pressure substantially greater than that at said suction port whereby pressure in front of a vane located in said transfer zone is greater than the pres- 1 5 sure behind said vane with the result that liquid flows through said clearance gaps past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane,

means for diverting the flow of liquid through a velocity reducing path to a zone of lower pressure than in front of said vane after it passes said leading edge and before it reaches the trailing edge of said vane, and

said diverting means comprising a longitudinal groove along at least one side of each of said vanes and conduit means connecting said groove with said lower pressure zone, said diverting means further including a valve operable to permit flow through said conduit means when said vane is in said transfer zone and to restrict flow through said conduit means when said vane is in said sealing zone.

15. The pump of claim 14 wherein at least a portion of said conduit means is located in the stator of said pump.

16. The pump of claim 14 wherein a first portion of said conduit means is located in said rotor and a second portion of said conduit means is located in said stator, that portion of said conduit in said stator including a section of restricted cross section operable to restrict the flow of liquid through said conduit and thus maintain a back pressure on the liquid in said groove.

17. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by said vanes,

transfer chambers defined between said vanes,

a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone and a sealing zone,

clearance gaps between said vanes and said stator,

means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure at said pressure port to a pressure substantially greater than that at said suction port whereby pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid flows through said clearance gaps past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane,

means for diverting the flow of liquid through a velocity reducing path to the chamber behind said vane after it passes said leading edge and before it reaches the trailing edge of said vane, and

said diverting means comprising a longitudinal groove along at least one side of each of said vanes and conduit means through the interior of said vane connecting said groove with a port on the trailing side of said vane, said port being so positioned on said vane that it acts as a valve to control liquid flow through said conduit means, said port being open to said transfer chamber on the trailing side of the vane when the vane is in the transfer zone and closed to said chamber on said trailing side when said vane is in said sealing zone.

18. The pump of claim 17 wherein said port consists of a large counterbore, located approximately medially of the length of the vane, said counterbore being connected to said conduit means by a bore of smaller cross sectional areas than said counterbore.

19. A vane type hydraulic pump comprising:

a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

transfer chambers defined between said vanes,

a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone and a sealing zone,

clearance gaps between said vanes and said stator, means for rotating said rotor so as to transfer liquid means for diverting the flow of liquid through a velocity reducing path to the chamber on the trailing side of the vane after it passes said leading edge and before it reaches the trailing edge of said vane, and

said diverting means comprising longitudinal grooves along two opposite sides of each of said vanes and conduit means through the interior of said rotor connecting said grooves with the chambers on the trailing sides of the vanes.

20. A vane type hydraulic pump comprising: a rotor having a plurality of vanes mounted for relative movement,

a stator presenting a cam surface and side walls for engagement by the outer ends of said vanes,

liquid transfer chambers defined between said vanes, a suction port and a pressure port at circumferentially spaced positions between said rotor and said cam surface, the space between said ports defining a transfer zone and a sealing zone,

clearance gaps between said vanes and said stator, means for rotating said rotor so as to transfer liquid from said suction port to said pressure port while increasing the pressure at said pressure port to a pressure substantially greater than that at said suction port whereby liquid pressure in front of a vane located in said transfer zone is greater than the pressure behind said vane with the result that liquid flows through said clearance gaps past the leading edge of the vane in an attempt to reach the lower pressure chamber behind said vane,

means for diverting the flow of liquid through a velocity reducing path to the chamber on the trailing sides of the vane after it passes said leading edge and before it reaches the trailing edge of said vane, and

said diverting means comprising a pair of longitudinal grooves along opposite sides of each of said vanes and conduit means through the interior of the rotor connecting said grooves with the chamber on the trailing side of the vanes, said diverting means further including a valve operable to permit flow through said conduit means when said vane is in said transfer zone and to restrict flow through said conduit means when said vane is in said sealing zone.

References Cited UNITED STATES PATENTS 1,898,914 2/1933 Vickers 103136 2,786,422 3/1957 Rosaen et al 103-136 2,809,595 10/1957 Adams et al 103136 2,967,488 1/1961 Gardiner 103-136 3,007,419 11/1961 Burt 103136 3,076,415 2/1963 Farron 103136 3,223,044 12/1965 Adams et al 103136 ROBERT A. OLEARY, Primary Examiner.

WILBUR J. GOODLIN, Examiner. 

8. A VANE TYPE HYDRAULIC PUMP COMPRISING: A ROTOR HAVING A PLURALITY OF VANES MOUNTED FOR RELATIVE MOVEMENT, A STATOR PRESENTING A CAM SURFACE AND SIDE WALLS FOR ENGAGEMENT BY THE OUTER ENDS OF SAID VANES, LIQUID TRANSFER CHAMBERS DEFINED BETWEEN SAID VANES, A SUCTION PORT AND A PRESSURE PORT AT CIRCUMFERENTIALLY SPACED POSITIONS BETWEEN SAID ROTOR AND SAID CAM SURFACE, THE SPACE BETWEEN SAID PORTS DEFINING A TRANSFER ZONE, CLEARANCE GAPS BETWEEN SAID VANES AND SAID STATOR, MEANS FOR ROTATING SAID ROTOR SO AS TO TRANSFER LIQUID FROM SAID SUCTION PORT TO SAID PRESSURE PORT WHILE INCREASING THE PRESSURE ON THE LIQUID AT SAID PRESSURE PORT TO A PRESSURE SUBSTANTIALLY GREATER THAN THAT 